Medical equipment for radiation therapy treats tumors tissue with high energy radiation. The dose and the placement of the dose must be accurately controlled to insure both that the tumor receives sufficient radiation to be destroyed, and that damage to the surrounding and adjacent non-tumorous tissue is minimized. Intensity modulated radiation therapy (IMRT) treats a patient with multiple rays of radiation each of which may be independently controlled in intensity and/or energy. The rays are directed from different angles about the patient and combine to provide a desired dose pattern. In external source radiation therapy, a radiation source external to the patient treats internal tumors. The external source is normally collimated to direct a beam only to the tumorous site. Typically, the radiation source consists of either high-energy X-rays, electrons from certain linear accelerators, or gamma rays from highly focused radioisotopes, though other types of radiation sources are possible.
Because the dose amount and dose placement need to be sufficiently controlled so as to ensure accurate patient treatment, the system itself needs to be commissioned properly at the outset and needs to be continuously monitored to ensure that the system is operating within the appropriate, and expected, parameters. When a system or machine is commissioned, the system characteristics are measured and compared against predetermined standards to configure the system and to ensure that the system is working within expected parameters. Commissioning includes consideration of total machine calibration, tuning the geometry of the beam delivered, and ensuring that the output and energy everywhere in the beam is equal, among other things. In some cases, individual systems are not calibrated with respect to each other, such that, in a way, each individual system stands alone in that variations in beam shape, strength, etc. can vary between machines. Each system is tuned to be within a manufacturing window, and a unique planning station model is generated. In effect, with each commissioning, you change the model to fit the machine.